1. Field of the Invention
This invention relates to a process for drying a wet cake of aminoguanidine bicarbonate under a CO.sub.2 -containing atmosphere at selected temperatures.
2. Brief Description of the Prior Art
Aminoguanidine bicarbonate (AGB) is a known chemical intermediate for many useful chemical products. For example, it may be converted into 3-amino-1,2,4-triazole, a known herbicide. AGB is a stable compound at ambient conditions whereas aminoguanidine is not stable under those conditions. Furthermore, AGB has advantageous properties as compared to other aminoguanidine salts. For example, it is insoluble in H.sub.2 O, which makes it easy to prepare in aqueous media.
Generally, AGB is made by reacting hydrazine or hydrazine hydrate with cyanamide or its salts (e.g. sodium or calcium) in the presence of an acid such as HCl, followed by adding a bicarbonate salt to the reaction mixture to precipitate out the AGB. The precipitated AGB is removed as a wet cake from the reaction mixture by filtration or centrifugation or the like. However, AGB is extremely heat sensitive when wet and discolors at temperatures as low as 35.degree. C. under normal drying conditions such as drying under air or nitrogen. Furthermore, drying AGB at temperatures below about 35.degree. C. results in long drying times and, in some cases, still results in undesirable amounts of residual moisture.
Accordingly, there is a need for an improved method of drying AGB whereby higher drying temperatures may be utilized without the undesirable discoloration.
It is an object of this invention to provide such an improved method for drying AGB.